Method and apparatus for fluid handling and separation



April 28, 1970 ed M'. COLEMAN 3,508,653

METHOD AND APPARATUS FOR FLUID HANDLING AND SEPARATION Filed Nov. 17, 1967 I'1E5-. l- TEE. PE-3 Prior 72 CHARLES M COLEMAN By. M

A I farneys United States Patent METHOD AND APPARATUS FOR FLUID HANDLING AND SEPARATION Charles M. Coleman, 958 Washington Road, Pittsburgh, Pa. 15228 Filed Nov. 17, 1967, Ser. No. 683,916 Int. Cl. B01d 21/00 US. Cl. 21083 16 Claims ABSTRACT OF THE DISCLOSURE A container assembly for effecting sealed separation of a fluid, such as blood, into a light phase and a heavy phase. A rigid tubular container adapted to receive the two-phase fluid has a resilient piston positioneid within the container in sealing contact therewith. The piston is adapted to be moved downwardly through the light phase of the fluid responsive to an applied force. The downwardly moving piston is adapted to permit upward flow of the light phase therearound. When the piston reaches the seal ing region, the applied force is withdrawn and the piston is adapted to establish a seal with the tubular container. In the preferred form of the invention, the piston is detachably secured to the underside of a resilient stopper which has an enlarged head portion disposed outside of the tubular container and a lower portion disposed partially within the container. The piston is adapted to be severed from the stopper by an applied centrifugal force which moves the piston downwardly through the light phase of the fluid.

Also a method of establishing sealed separation of blood into light and heavy phases by providing a tubular container having the separated two phases and a resilient piston seated within the container above the fluid. The piston is moved downwardly through the light phase responsive to an applied force and simultaneously, the light phase fluid moves around the piston and upwardly. The downward movement of the piston is stopped at a position generally between the two phases, responsive to termination of the applied force, and a seal is thereby established. The moving force is preferably centrifugal force.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a method and apparatus for effecting sealed separation of a two-phase fluid within a single container. More specifically, it relates to the separation of blood serum or plasma from the blood cells.

Prior art The clinical evaluation of biological fluids such as blood, has long been an important part of our medical system. As such evaluations present information with regard to a patient which would not be otherwise available, this type of an evaluation is an important part of the examination and treatment of a substantial number of individuals obtaining medical attention. Accurate clinical evaluation often means the difference between a healthy, productive life and extended convalescense, permanent disability or death.

'With respect to blood analysis, the total annual number of such tests is increasing at a very substantial rate.

A recent report by the United Sates Public Health Service estimates that unsatisfactory performance in the measurement of blood serum electrolytes is demonstrated by 20 to 30% of the laboratories in this country.

In conventional practice, a blood sample is withdrawn from an individual and enters a collecting tube. The collecting tube may then be allowed to sit for a period of Patented Apr. 28, 1970 about one half hour, during which a partial separation of the blood cells, the heavy phase, from the blood serum the light phase, is partially effected. The specimen is then placed in 'a centrifuge for completion of the separation. The separated serum is then analyzed. Alternatively, an anticoagulant may be added to the blood specimen which may then be centrifuged without prior gravitational separation. This will result in the separation having a cell phase, the heavy phase, and a lighter phase of blood plasma. The lasma may then be employed for purposes of testing.

In analyzing blood serum or blood plasma, the tests may include an examination to determine the percentage constituency of one or more of the following ingredients: glucose; cholesterol; calcium; inorganic phosphorus; bilirubin; albumin; protein; uric acid, urea nitrogen; lactic dehydrogenase; alkaline phosphatase protein-bound iodine; serumglutamic-oxalacetic transaminase; and other ingredients. As each of these will generally bear a direct. relationship to the physical state and health of the individual being tested, it is of course, essential that complete accuracy be obtained.

One of the prime requisites is the maintenance of completely sterile conditions. Most conventional systems require that the serum or plasma be removed from the collection container after separation and transferred to another container. There are several means by which the plasma or serum is conventionally removed from the first container. This is frequently accomplished by decanting, siphoning or the use of a vacuum needle. This presents the double hazard of exposure of th serum or plasma to unsterile conditions, as well as the hazard of the second container not being completely sterile.

An additional hazard in such systems arises from the need to identify the specimen with the individual through the entire clinical process. It will be appreciated that when the serum or plasma is removed from the collection tube and placed in another container, the hazard of mismarking or loss of true identity of the donor is present.

Another hazard encountered in the transfer of serum or plasma is the obvious one of spillage on laboratory personnel thereby exposing them to blood which may contain materials harmful to the health. Frequently such blood samples will consist of hepatitic or syphilitic serum which could infect personnel contacting the serum.

One of the major problems encountered with respect to such testing is the fact that, as the number of such tests increases, more and more delay is encountered between the time that the specimen is extracted from the patient and the time that the analysis is made. It is known that this delay may be very harmful and may produce inaccurate results with respect to the percentage of any constituent present in the blood. It is known, for example, that as the serum-cell (or plasma-cell) separated blood is standing, glucose will travel from the serum downwardly into the cells. When the serum is subsequently removed and tested for glucose content, an artificially low reading will be obtained. Thus, an individual having diabetes may have a test result indicating a satisfactory glucose blood component, when in fact, the component is present in undesirable or even dangerously high amount. Also, the enzymes lactic dehydrogenase and glutamicoxalacetic transaminase leak out of the cells with the passage of time and enter into the serum. This is also true of the cation potassium.- In addition, it is important that carbon dioxide and blood pH values are maintained constant.

In the interest of obtaining accurate test results, which are often vital to proper treatment, this sort of inaccuracy cannot be tolerated. It should be noted that such delays are not only present in hospitals having increased demands being made upon their laboratory facilities, but also with respect to physicians and clinics not having such facilities. This latter group are required to somehow arrange for transport of the specimens to laboratory facilities.

Several means of obtaining a specimen or blood sample from an individual in a sterile fashion have been known in the art. In the system illustrated in United States Patent 2,460,641, a glass tube has one end integrally closed and the other end closed by a stopper having a pair of axial recesses entering the top and bottom of the stopper. A cup-like container having a double ended hollow bored needle with one end terminating within the cup and the second end terminating on the outside of the cup is provided. In obtaining a specimen, the stoppered end of the glass tube is placed within the glass cup and the needle end extends through the stopper intermediate the two axial recesses and into the tube. The outwardly disposed end of the needle is then injected into the individual. As the stoppered tube has been evacuated, the individuals blood pressure causes the blood to flow through the needle into the tube. When the desired quantity of blood has been extracted, the needle is extracted from the individual and the cup removed from the tube, thereby providing a stopper sealed sterile container housing the blood sample.

It has also been known in the taking of blood samples, to provide a collecting tube having a stopper or closure communicating with the tube interior and supporting a needle adapted to be inserted into the individual giving the specimen. Two such collecting devices having manually operable valves housed in the container closure are illustrated in United States Patents 2,518,165 and 3,308,890. In United States Patent 2,518,165, the container extension is a rubber tube which contains a glass ball. Suitable forces applied to the exterior of the rubber tube result in the creation of an opening between the glass ball and rubber tube permitting flow therethrough. In the valve for-m illustrated in United States Patent 3,308,809, the stopper has a preformed slit which is normally closed, but may be opened by compressive force applied to the exterior of the stopper member.

While these prior art devices may result in Obtaining a blood specimen from an individual without contamination, the subsequent separation of the serum or plasma from the cells and removal of the serum or plasma for purposes of analysis present the problems discussed above.

It has been suggested to employ a multiplicity of relatively small plastic particles of specific uniform size, shape and specific gravity in order to establish a barrier between the serum or plasma and the cells. In such an arrangement, the loose materials are placed into the blood sample prior to phase separation and the tube is subjected to a normal centrifugal separating force. These plastic particles tend to locate at a specific position withir: the tube and establish a barrier between the serum or plasma and the cells. This system, however, will tolerate no subsequent jarring or unusual motion, as this will tend to destroy the barrier. Thus, there is the risk that any unusual motion will destroy the barrier in an unobservable fashion and yield inaccurate chemical readings. As to those individuals not having laboratory facilities on the premises, it is necessary to transport the samples either through the mail or by some other transportation system. The barrier formed by these particles would not withstand the jarring movements inherent in these transportation methods.

SUMMARY OF THE INVENTION The above discussed problems have been eifectively solved by the apparatus and method of this invention. The container assembly of this invention provides an elongate rigid tubular container adapted to serve as a specimen collector and also eliminate the need for transfer to a second container. The container has a resilient stopper with an enlarged head portion disposed outwardly of the tube and a lower portion inserted within the tubular container. A resilient plunger is positioned within the tube closely adjacent the resilient stopper. The resilient plunger is in sealing contact with the inner surface of the tubular container. The plunger is adapted to move downwardly through the serum or plasma phase of the blood responsive to an applied force and simultaneously permit movement of the plasma or serum around the plunger upwardly. When the plunger has moved downwardly to the interface between the plasma and serum on the one hand, and the cells on the other, the force is Withdrawn and the plunger effects a seal between the two phases. In the preferred form of the invention, the plunger is detachably connected to the bottom of the stopper. This may be accomplished by an independent fastener, an adhesive, an integrally molded connector, or by physical interengagement. The connection between the stopper and the plunger is such that neither insertion of a hollow needle in order to introduce the blood specimen into the tubular container nor initial centrifuge action in order to separate the blood into the serum or plasma and cells will sever the connection. A subsequently applied increased centrifugal force will cause the desired separation. The resilient plunger should be of larger diameter than the interior of the tubular container, in order to effect a tight seal.

With the apparatus of this invention, an eifective seal is obtained by positioning a unitary sealing member between the cells and the plasma or serum. The seal is of a permanent nature. Also, sterility of the specimen is maintained throughout. The risk of contamination through improperly cleansed glassware is eliminated as the container of this invention is disposable. Also, as the transfer of the specimen to a second container is eliminated, the risk of loss of identity as to the individual source of the specimen, as well as contamination of laboratory personnel is very substantially reduced.

The method of this invention involves providing an elongate tubular container having a resilient piston or plunger disposed within the tubular container. Movement of the resilient piston downwardly through the light blood phase is effected by an applied force to thereby simultaneously establish flow of the serum or plasma upwardly around the piston, intermediate the piston and interior tubular container wall. A seal is established between the two blood phases by terminating the application of force, thereby stopping the downward movement of the piston and establishing a sealed relationship between the tubular container and the piston.

As the seal effectively isolates the two blood phase components and prevents material transfer and chemical interaction, therebetween, the tube may be stored indefinitely without detrimental aifect on the specimen. If shipping is desired, a stopper on the top of the tube will serve as a seal to prevent contamination or loss of the serum or plasma. Where transportation is not contemplated, the stopper preserves sterility of the serum or plasma until such time as the tube is inserted into the analyser equipment.

It is an object of this invention to provide apparatus and method for the sterile extraction, storage and analysis of biological fluids such as blood.

It is another object of this invention to provide apparatus and a method for effectively sealing the blood serum or plasma from the blood cells in order to prevent chemical interaction and transfer of one phase material to the other.

It is another object of this invention ot provide a method and apparatus for blood analysis wherein subsequent to the centrifugal separation of the serum or plasma from the cells an increased centrifugal force applied for a brief moment is all that is required in order to automatically provide an effective unitary seal intermediate the two phases, which seal is adapted to maintain its integrity throughout any sort of subsequent handling which might be required.

It is another object of this invention to provide a com pound stopper and sealing piston which are adapted to automatically separate under the influence of an applied force, thereby permitting the piston to travel through the serum or plasma and establish a seal at the interface between the serum or plasma and the cells.

It is yet another object of this invention to provide apparatus and method for the clinical handling of blood samples without risk of loss of the donors identity without risk of contamination, while maintaining economy and simplicity as well as eliminating the need for retraining laboratory and medical personnel.

It is yet another object to provide such a system wherein duplicate glassware is not required for each test performed and the single piece of glassware employed is disposable, thereby eliminating an additional potential sterility hazard.

Other objects and advantages of this invention will be understood from the following description of the invention on reference to the illustrations appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 illustrates a prior art device adapted for the sterile collection of a blood sample from an individual.

FIGURE 2 illustrates a tubular container having a resilient plunger disposed above the separated plasma or serum and cells.

FIGURE 3 is similar to FIGURE 2 but illustrates the piston having moved part way through the blood serum or plasma.

FIGURE 4 illustrates the piston in final sealing position immediately above the top surface of the cell phase.

FIGURES 5-7 illustrate a different embodiment of the invention in stages corresponding generally to those illustrated in FIGURES 2-4.

FIGURES 8 and 8a illustrate the preferred form of compound stopper-piston structure contemplated by this invention.

FIGURE 9 illustrates another preferred form of compound stopper-plunger contemplated by this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more specifically to the drawings with particular attention to FIGURE 1, this figure' illustrates a sterile blood collection device known in the prior art. The device has a collection tube 2 sealed by means of stopper 4 extending into it, which stoppered collection tube 2 extends into cup-shaped member 6. At the closed end of cup-shaped member 6, is mounting bracket 8 to which is connected a hollow double end pointed needle 10. The needle 10 has a needle end 12 extending outwardly of the cup-shaped member and a needle end 14 extending into the cup-shaped member 6. In obtaining a blood sample, the needle end 12 is inserted into the individual and the needle end 14 is pushed through stopper 4 to communicate with the interior of collection tube 2. As the sealed collection tube has been previously evacuated, blood will flow from the individual through the hollow double pointed needle into the collection tube 2. When the desired amount of blood has been collected from the individual, the needle end 12 is withdrawn and the collection tube 2 is withdrawn from the cup-shaped member 6 thereby removing needle end 14 from communication with the interior of collection tube 2. The resiliency of the stopper 4 causes the opening through which needle end 14 passes to reclose. This system, therefore, yields a sterile stoppered tube containing a blood specimen.

One of two procedures is then followed depending upon whether one wishes to obtain blood serum or blood plasma. It blood serum is being sought, the stoppered tube is allowed to stand for a period of about 20 to 40 minutes in order to effect some phase separation. The tube is then placed in a centrifuge which completes separation into two blood phases. Disposed at the bottom of the tube will be the heavy phase which consists of the packed blood cells and disposed at the top of the tube will be the light phase which is the serum.

In the interest of simplicity of description, the term light phase will be employed to refer to the low density portion of the fluid and the term heavy phase will be employed to refer to the high density portion of the fiuid. As one of the main purposes of this invention is to effect sealed separation of the light phase disposed in the upper portion of the container from the heavy phase disposed in the lower portion of the container, the seal should be effected at a position not lower than the interface of the two phases, and reference herein to such sealed separation shall refer to such a seal. While, as is apparent, sealing above the interface will serve only to reduce the amount of light phase disposed above the seal and available for laboratory use, sealing below the interface will produce the serious problems resulting from chemical interaction and/ or physical interchange between the two phases.

If, on the other hand, it is sought to isolate plasma, an anticoagulant must be introduced into the tube in order to prevent blood clot formation. This tube may then be centrifuged immediately without waiting for an initial separation. The result will be a heavy phase consisting of cells at the bottom of the tube and a lighter phase consisting of plasma at the top of the tube.

One form of separation through use of the system of this invention is illustrated in FIGURES .24. It is seen in FIGURE 2 that the tubular container 20 houses a heavy phase 22 which as shown, are blood cells and a lighter phase 24 which may be either blood serum or plasma. Secured within the tube in overlying relationship with respect to the blood, is a resilient plunger or piston 26. The resilient plunger 26 has a diameter greater than the interior diameter of the tubular container 20. It, therefore, is in compression and provides a seal between the interior of tubular container 20 and the exterior. Thus, the blood in the position indicated in FIGURE .2 is maintained in sterile condition by means of compressed resilient plunger 26.

In initiating sealed separation of the two phases, a downwardly directed force is applied to the plunger 26 to initiate movement of the plunger 26 through light phase 24. In the arrangement selected for illustration, a firm but gentle force is applied manually by a rigid rod 30 which has its lower end in contact with the upper surface of plunger 26 and its upper end extending out of tubular container 20. As the applied force causes plunger 26 to move downwardly, as is shown in FIGURE 3, the fluid pressure of the light phase causes the light phase to deform plunger 26 and flow around the plunger 26 and upwardly between the plunger and the interior surface of tubular container 20. In effect, the applied force causes the resistant fluid pressure to increase to sufficient magnitude to partially compress plunger 26 thereby relieving the pressure and permitting movement of light phase 24 around plunger 26.

Should it be desired, the plunger 26 could be provided with a valve type opening which would permit passage of the upwardly moving light phase through the plunger 26 in lieu of, or in addition to, passage therearound. An axial passageway through the plunger 26 could be provided with a valve element, such as a flap valve, for example.

When the piston or plunger 26 has moved downwardly to the point where the upper surface of the heavy phase 22 is adjacent the bottom of the plunger 26, the applied force is withdrawn thereby causing the downward movement of plunger 26 to stop. This results in expansion of piston or plunger 26 into sealing relationship with the interior surface of tubular container 20. In this position, further transfer of blood materials from one side of the plunger 26 to the other is prevented, as is chemical interreaction between the two phases. Also, obtaining true values of carbon dioxide and blood pH is facilitated. Rod 30 is then withdrawn and a stopper may be inserted in order to complete sealed compartmentalization of the tube.

It will be appreciated that this effective sealing action eliminates the need to be concerned with the length of subsequent storage time. Also, the stopper inserted'into the top of the tube prevents contamination from external sources between the time at which the seal was effected and the time when the analysis will be made. At such time, the stopper may be removed and the serum tested directly in the container 26. There has been no opportunity for contamination of either the blood serum or plasma or personnel resulting from transfer of the blood sample or portions thereof to another container. After the tests have been completed, the container 20 may be discarded, thereby eliminating the contamination risk presented by improperly cleaned re-usable containers.

Inherent in the centrifugal separation of the two phases is the adherence of particles of the blood cells to the upper portion of the interior surface of the tubular container 20. The downward moving plunger 26 will loosen a substantial proportion of such cells and move them downwardly into the heavy phase 22.

In the form of container assembly illustrated in FIG- URES 7, a container 40 contains a heavy phase which consists of blood cells 42 and a light phase which consists of blood cells or serum 44. A resilient piston 46 and resilient stopper 48 are provided. The resilient piston 46 has an expanded diameter larger than the internal diameter of tubular container 40. In the position shown, inserted into the tubular container, the piston 46 has been compressed and, therefore, establishes a seal in cooperation with container 40. The stopper 48 has an enlarged portion or head 50 which is disposed outside of the container and serves to limit the extent of entry of the stopper into the container 40. The stopper 48 also has a lower portion 52 of reduced diameter, which is inserted into the container 40 and preferably is in compression when so inserted. The stopper 48 is also provided with an axial recess 54 for reasons which will be described below.

In the preferred use of the container assemblies shown in FIGURES 5-7, a sterile evacuated tube is provided with the stopper 48 and piston 46 positioned as shown in FIGURE 5. Blood may be collected in the tube Without removing stopper 48 by means such as that illustrated in FIGURE 1. Recess 54 reduces the amount of stopper thickness through which the needle must pass in order to gain communication with the interior of container 40. After the blood sample has been introduced into the sealed container 40, the sample is subjected to centrifugal separation, with or without a period of prior settling. As has been indicated above, in order to prevent chemical interaction of the two blood phases, it is essential that a seal be promptly established between the two phases, as soon as possible after separation has been effected.

FIGURE 5 illustrates the apparatus immediately after centrifugal separation of the phases has been effected. The centrifugal force is then increased to such an extent, that the piston is caused to move downwardly with simultaneous movement of the light phase 44 around and generally upwardly with respect to the descending piston 46. When the piston has moved downwardly to the point where its lower surface reaches the upper surface of the cell phase, 42, the centrifugal force is terminated in order to stop the downward movement of piston 46 and thereby place it in sealed position separating the cells 42 from the serum or plasma 44. In the 8 view illustrated in FIGURE 6, the piston has traveled part way through the serum or plasma and in FIGURE 7, the piston is shown in its final sealing position.

It may be observed in FIGURE 7, the container 40 has a sealed lower compartment housing the cells 42 and a sealed upper compartment housing the plasma or serum 44. As the stopper 48 remains in sealing position throughout the process, the serum or plasma 44, as well as the cells 42 remain in sterile sealed condition. Throughout the entire operation, from point of collection to the point of sealed compartmentalized separation, there has been no transfer of the blood specimen or anyportion thereof, out of the collection tube, nor has there been any exposure of the blood specimen or any portion thereof, to the potentially contaminating air disposed outside of the container. Immediately after phase separation, sealing between the two phases has been effected. The tube illustrated in FIGURE 7, therefore, contains two sterile blood phases 42, 44 effectively sealed from exposure to each other and effectively sealed from exposure to external contamination. The container 40 may be stored for an indefinite period of time without producing any detrimental chemical interaciton between the two phases. Also, the container may be transported, through the mail or otherwise, without there being any risk of contamination or loss of accuracy of the results of the subsequent clinical analysis of the blood specimen as a result of such shipment.

In addition to employing a hollow needle as a means of extracting blood from an individual in order to obtain the desired specimen, small quantities of blood are frequently obtained by making a small puncture in an individuals finger, ear lobe or other easily accessible place. The apparatus employed in such extractions is generally an elongate tubular container having a vented stopper at one end and being open at the other. The open end is placed against the punctured opening in the individual, and through capillary seepage, the blood is drawn into the tube. The vent permits the air in the tube to be discharged as the blood enters the tube. The opened end of the tube is then sealed by a cap member and the vented stopper is removed from the other end of the tube which is then sealed by a stopper. While the method of introduction of the blood into the tubular container, as well as the quantity of blood taken, vary with this type of system, the apparatus of this invention is equally applicable to such systems.

As has been indicated above, the piston 46 is placed inside the tube in underlying position with respect to the stopper 48. In the preferred form of the invention, the piston 46 is detachably secured to the stopper 48. The piston may in fact be a separate entity restrained against premature downward movement solely by engagement between the piston and container and not be attached to the stopper 48. Increased control over piston migration and the handling of the stopper 48 and piston 46 as a unit, are facilitated by the interconnection of the two. In the form shown in FIGURES 57, the piston 46 may be secured to the stopper 48, by an adhesive 56 shown in exaggerated thickness in FIGURE 5. Alternatively, the piston 46 may be attached to the stopper 48 by separate fastening means. In the form shown in FIGURES 8, 8a the piston 146 and stopper 148 have been molded as a unit and have integral connecting rod 150. Connecting rod is adapted to resist downward movement of the piston prior to fracture at a predetermined force level in order to free piston 146 for downward movement within the tube.

In the combination illustrated in FIGURE 9, the stopper 60 has an axial recess 62 disposed within the bottom of the stopper. The piston 64 has an upstanding boss 66 extending upwardly from the top surface thereof. The boss 66 passes into recess 62 to establish detachable engagement between stopper 60 and piston 64.

Regardless of the form of attachment between the piston and stopper, if they are to be inserted into the tube prior to collection of the blood sample, the connection between the piston and the stopper should be sufficiently strong to resist severance upon insertion of the needle through which the blood specimen is introduced into the container. Also, when the collected specimen is centrifuged in order to separate the two blood phases, the connection should preferably be able to resist separating under the influence of the initial centrifugal force. Thus, in the preferred form, after a centrifugal force has been applied to separate the blood into two phases, an increased centrifugal force is applied to sever the connection to detach the piston from the stopper and move the stopper downwardly through the light phase.

Numerous piston designs may \be employed with this invention. All that is required is that the piston have resiliency and have at least a portion of greater diameter than the internal container diameter. This enables the piston to be placed, under compression, within the tube and thereby retain a seal. The piston may take the form of the solid resilient cylinder, as is illustrated in FIG- URES 5-7. In the form of piston shown in FIGURES 2-4, the piston 26 has a tricuspid shape. The general outline is that of a cylindrical piston, however, portions of the material have been removed from the cylinder to establish an upper sealing surface 70 and a lower body portion 72. In the plunger 64 shown in FIGURE 9, the upper portion serves as a sealing portion and the plunger is tapered downwardly therefrom.

Considering in greater detail the molded stopper 146 and piston 148 illustrated in FIGURE 8, it is seen that the upper portion of the piston 148 has an integral disc 152 which has a container contacting surface adapted to engage the container interior in order to effect a seal. As the remainder of the piston 148 is of smaller diameter than the disc, the downward movement of the piston, effected after severance of connector 150, results in the fluid passing around the major portion of the piston without deforming the same and the deformation occurring solely across the disc 152. Numerous additional suitable piston configurations may occur to those skilled in the art.

One additional feature which facilitates efficient performance is present in FIGURES 8 and 8a. FIGURE 8a is a bottom plan view of the assembly of FIGURE 8. As is seen in FIGURE 5, intermediate the bottom of piston 46 and top of light phase 44 is a space 80. Generally, this space 80 will contain some air and gases evolved from the blood sample. The stopper-piston combination of FIG- URES 8 and 8a illustrate a preferred means of venting these gases and eliminating a potential retarding affect they might have on the downward moving piston through a bouyancy effect. The piston 148 is provided with a main passageway 82 and supplemental passageways 84 which communicate with vent opening 86. As the piston 148 descends, gases move upwardly within passageway 82, disposed generally centrally with respect to the longitudinal axis of the piston 148, and build up sufiicient pressure to pass through vent 86 and escape to a position underlying disc 152. Disc 152 is provided with a pressure equalizing channel 88 which is adapted to open responsive to a build up of gas pressure and permit passage of gas therethrough. It will be appreciated that this supplemental gas relief means facilitates reduced resistance to the downward movement of piston 148 toward the sealing position. Should it be desired to place a valve for the passage of the light phase within the piston 158, passageway 82 may pass completely through the plunger and the valve may be positioned therein.

With respect to the material from which the stopper is to be made, it generally should possess sufiicient resiliency to permit compression to establish a seal between the container and the piston and should be deformable during downward movement responsive to the applied force and the resultant fluid pressure. Plastic, rubber and various combinations thereof, have been found to be suitable for this purpose. Styrene-butadiene having a tensile strength of about 250 1000 lb./in. has been found to be satisfactory, for example. For purposes of displacement of the piston by an applied centrifugal force and stopping of the movement at'the desired position within a two phase blood fluid, it is preferred that the piston have a specific gravity between that of the two blood phases. A suitable specific gravity would be about 1.045 to 1.09, and a durometer hardness of about 15 to 45, but these are not essential. For example, a larger centrifugal force could be employed with a lighter piston or a heavier piston could be employed with a lower centrifugal force. Also, the material of the piston should be nonporous with respect to the serum or plasma and preferably should be nonporous with respect to the blood cells. In general, it is contemplated that the specific gravity of the piston will be between the specific gravity of the serum or plasma and the cells, thereby, in effect, creating an automatic stopping of the piston at the appropriate phase dividing line, but as has been indicated above, this is not essential.

Where the material is of limited resiliency, it is preferable to provide a recess within the piston to facilitate deformation thereof.

The method of this invention contemplates providing a sealed elongate tubular container housing a light blood phase and a heavy blood phase with a resilient piston initially disposed within the container above both the respective blood phases. The resilient piston is moved downwardly through the light blood phase responsive to an applied force and is thereby deformed to establish upward flow of the light phase around the piston. The piston is stopped at the desired interface and the resiliency of the piston establishes a seal between the two phases. The force establishing the downward movement is preferably centrifugal force and the piston is preferably initially detachably secured to an overlying stopper with detachment being effected prior to moving the stopper downwardly.

It will be appreciated that the apparatus and method of this invention, therefore, provide an effective economical means of employing a container assembly for the extraction, phase separation and compartmentalized sealing of the respective blood phases, all within a single container. The invention facilitates the automatic establishment of a seal through application of an increased centrifugal force immediately following the centrifugal separation of the two phases. In a preferred form, the sealing plunger is detachably secured to an overlying stopper which results in the container being, from the outset, sterile, and having the container ultimately compartmentalized with the two blood phases separated from each other and the overlying stopper serving to separate the container contents from the exterior contaminating atmosphere. As a result of the lack of need to transfer the blood from the collecting container into another container and mark the second container for identification purposes, the loss of sterility as well as the loss of identity of the donor and hazardous spillage on laboratory personnel is entirely eliminated. Also, the risk of chemical contamination affecting test results and loss of sterility through improper cleaning of reusable glassware as well as the economics of not requiring two independent pieces of glassware for each sample taken are obtained. As the two phases are properly separated and chemical interaction is thereby prevented, indefinite storage without the hazard of producing inaccurate readings as to the amount of a given chemical constituent present in the serum or plasma is eliminated. Also, shipment to other locations than the one in which the sample was taken is facilitated without the need to be concerned with inaccuracies produced by such handling and delay. Also, should it be desired to re-examine the same 1 1 specimen to verify the initial results, storage within this container for an indefinite period of time may be accom; plished and this end may be attained.

It will be further appreciated that this invention results in no need to retrain medical personnel in the methods of blood exraction and would require no new skill in regard to the handling and analysis of the blood obtained. Finally, the prompt and permanent seal established by the compressed resilient member effectively terminates the risk of chemical communication and material interchange between the phases, whether the container be handled gently, be subject to the agitation encountered in normal transportation and mailing, or receive any unusual handling short of destruction of the container itself.

While for purposes of clarity of illutration, specific piston designs and specific means for securing the piston to overlying stoppers have been disclosed, it will be apparent that other designs could function efiiciently with the apparatus and method of this invention. For example, the disc 152 illustrated in FIGURE 8 could be provided at the bottom of piston 148 in lieu of the top or at a position intermediate the top and bottom. Also, where the stopper-piston combination is employed, and they are connected integrally as shown in FIGURE 8, several connections 150 could be provided. Other minor modifications not departing from this invention will occur to those skilled in the art.

Throughout the description, reference has been made interchangeably, to withdrawal or termination of the applied force. With respect to the embodiment illustrated in FIGURES 24, this reference is to stopping the application of a downwardly directed force applied through rod 30. With respect to the embodiment employing centrifugal force, additional factors must be considered. The movement of a given piston is, in general, a function of the specific gravity of the piston and the magnitude of the centrifugal force. For a given piston of a fixed specific gravity, a given centrifugal force will move the piston to a given position and no further. In effect, once that position has been reached, the affect of the centrifugal force is withdrawn or terminated even though the centrifuge may continue to run and the centrifugal force continues to be applied. It is in this sense that withdrawal or termination of the applied force is to be interpreted. There is, therefore, no need to effect immediate shutoff of the centrifugal force.

For clarity of illustration the sequence of operation employing this system has been stated to be first phase separation of the blood and subsequently downward movement of the piston. Downward movement of the piston within space 80 (FIGURE 5) but not penetrating into the blood, is permitted during phase separation, and will not interfere with the performance of the apparatus and method of the invention and is contemplated within the scope of the invention.

While reference has been made repeatedly to the piston moving downwardly through the fluid, such usage is, of course, intended to refer to movement into the container regardless of container orientation.

Whereas, particular embodiments of the invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that numerous variations of the details may be made without departing from the appended claims.

I claim:

1. A container assembly for effecting sealed separation of a fluid into a light phase and a heavy phase comprising,

an elongated rigid tubular container adapted to receive a sealing closure having a resilient transversely continuous wall,

said sealing closure disposed in sealing engagement with said container,

a closed fluid receiving chamber defined by said container and said sealing closure,

a deformable piston positioned within said fluid receiving chamber underlying and closely adjacent to said closure,

said deformable piston closure having an uncompressed transverse dimension greater than that of the interior of said tubular container,

said deformable piston in initial sealing contact with the inner surface of said tubular container,

said piston adapted to move downwardly in said fluid receiving chamber through said light phase of said fluid responsive to a force applied through means not in direct physical contact with said piston with said light phase of said fluid flowing upwardly,

said piston adapted to stop moving downwardly within said fluid receiving chamber and assume final sealing contact with the inner surface of said tubular container,

said container closure is a stopper having a lower portion disposed within said container,

said piston is resilient,

said fluid is blood,

said resilient piston is generally cylindrical and has an uncompressed diameter greater than the internal diameter of said tubular container,

said assembly having piston restraining means contacting said piston for resisting downward movement of said piston,

said resilient piston is adapted to permit upward flow of said light phase therearound, and

said piston is adapted to be moved downwardly Within said container responsive to an applied centrifugal force.

2. The container assembly of claim 1 wherein,

said elongated container is of substantially uniform diameter intermediate its ends,

said resilient stopper has an enlarged head portion disposed outwardly of said container,

said resilient stopper has an axial recess in said head portion of said stopper for facilitating introduction of said blood into said tubular container by means of a hollow needle which enters said axial recess and penetrates through and resiliently deforms both said stopper and said piston,

said piston restraining means detachably connects said resilient piston to said stopper and said piston is adapted to be detached from said stopper by said applied centrifugal force, and

said connection between said stopper and said piston is sufficiently strong to resist severance during the introduction and removal of said hollow needle.

3. The container assembly of claim 1 wherein,

the lower portion of said resilient stopper is tapered downwardly,

said piston and said stopper are composed of rubber,

said piston restraining means includes a portion of the interior of said container in contact with said piston,

said piston has an upper disc portion and a depending underlying body portion of lesser diameter but greater axial extent than said disc, and said disc sealingly engages the inner surface of said tubular container.

4. The container assembly of claim 2 wherein,

said piston restraining means is adhesive means interposed between said piston and said stopper providing a severable connection between said stopper and said piston.

5. The container assembly of claim 2 wherein,

said piston restraining means is molded integral connecting means providing a severable connection between said stopper and said piston.

6. The container assembly of claim 3 wherein,

said piston has a specific gravity of about 1.045 to about 13 7. A method of establishing sealed separation of blood into a light phase and a heavy phase within a unitary container, comprising,

providing a sealed elongate unitary tubular container having a light blood phase and a heavy blood phase with a resilient piston disposed within said container in sealing contact with the inner surface thereof at a position above said light phase,

moving said resilient piston downwardly within said unitary sealed container through said light blood phase responsive to force applied by means not physically contacting said piston to thereby establish flow of said light blood phase upwardly within said sealed unitary container, and

establishing a seal between the inner surface of said container and said resilient piston not lower than a position intermediate said phases by stopping said downward movement of said piston by terminating said applied force.

8. The method of claim 7 including prior to establishing said seal, centrifuging said blood in order to establish separation of said phases,

said piston moving force is a centrifugal force,

establishing said upward flow of said light blood phase within said sealed unitary container solely around said downwardly moving piston,

subsequently to said phase separation and downward piston movement establishing a final seal, and

maintaining said container sealed from physical communication with the outside environment until after said final seal is established.

9. The method of claim 8 including,

continuously during the process providing a Sealed sterile chamber within said container with said phases disposed therein kept out of contact with the atmos phere, and establishing a final seal between said piston and the inner surface of said container which seal resists mechanical and chemical interaction between said phases.

10. The method of claim 9, including,

providing a stopper sealed to said container in overlying position with respect to said piston,

prior to separation of said phases, said piston is detachably secured to said overlying stopper which is partially inserted into said container,

said centrifugal force applied for separation of said phases is insuflicient to separate said detachably connected stoppers, and

said centrifugal force applied for moving said piston is sutficient to separate said stopper and said piston.

11. A unitary resilient piston for use in effecting centrifugally established sealed separation of a blood specimen into two phases within a tubular container comprising,

an integral sealing portion with a container contacting surface spaced transversely outwardly of the longitudinal central axis of said piston and adapted to sealingly engage the inner surface of said tubular container,

a resilient generally cylindrical body portion integrally formed with and of a smaller diameter than said integral sealing portion disposed in close axial proximity to said integral sealing portion,

said longitudinal axis of said piston adapted to be substantially aligned with the longitudinal axis of said tubular container when said piston is inserted into said container,

passageway means defined within said piston facilitating passage of gases but resisting the passage of liquids through said piston,

said passageway means having an axial recess communicating with and terminating at the bottom of said piston, and

said axial recess being shorter than the axial length of said piston.

12. The piston of claim 11 wherein said integral sealing portion is substantially symmetrical with respect to said longitudinal axis of said piston,

said axial recess having an upper extremity at a portion spaced below the upper extremity of said generally cylindrical body portion, and

said diameter of said generally cylindrical body portion is closer to the diameter of said sealing portion than to the diameter of said axial recess.

13. The piston of claim 12 wherein said generally cylindrical body portion depends downwardly from said integral sealing portion and has an upper sector of smaller diameter than the remainder of said body portion,

said axial recess is substantially vertically disposed and communicates at its upper extremity with a substantially horizontal passageway which extends radially outwardly to the surface of said body portion, and

said piston has a specific gravity of between about 1.045

to about 1.09.

14. A resilient piston assembly for use in effecting sealed separation of a blood specimen into two phases within a tubular container, comprising,

an integral sealing portion with a container contacting surface spaced transversely outwardly of the longitudinal central axis of said piston and adapted to sealingly engage the inner surface of said tubular container,

said longitudinal axis of said piston adapted to be substantially aligned with the longitudinal axis of said tubular container when said piston is inserted into said container,

passageway means defined by said piston permitting passage of gases but not liquids through said piston, said passageway means having an axial recess communicating with and terminating at the bottom of said piston,

a stopper member having a head portion and a depending lower portion,

at least a portion of said lower section having a substantially continuous transverse sector,

means for detachably securing said piston in underlying relationship with respect to said stopper, and

said head portion having a larger transverse dimension than said lower portion. 15. The piston of claim 14 wherein said stopper and said piston are integrally molded as a unitary structure, and

said means for detachably securing said piston has at least one integrally formed molded connecting member.

16. The piston of claim 14 wherein said means for detachably securing said piston is an adhesive material.

References Cited UNITED STATES PATENTS REUBEN FRIEDMAN, Primary Examiner J. W. ADEE, Assistant Examiner US. Cl. X.R. 210-516; 233-26 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,508,653 April 28, 1970 Charles M. Coleman It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 15, "positioneid" should read positioned line 66, "Sates" should read. States Column 7, line 16, "container 26" should read container 20 Column 9,

line 67, "piston 158" should read piston 148 Column 12, line 6, after "piston" cancel "closure".

Signed and sealed this 12th day of January 1971.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

